Method of preparing stencils for use in stencil duplicating



1956 NOBORU. HAYAMA ETAL. 3,267,847

METHOD OF PREPARING STENCILS FOR USE IN STENCIL DUPLICATING Filed Aug.5. 1964 FIG.'4

hm W INVE TOR:

BY W

United States Patent 3,267,847 METHOD OF PREPARING STENCILS FOR USE INfiTENClL DUPLICATING Nohoru Hayama and Kazuo Ishijima, Tokyo, Japan,assignors to Riso Kagaku Corporation, Tokyo, Japan, a corporation ofJapan Filed Aug. 3, 1964, Ser. No. 387,098 Ciairns priority, applicationJapan, Aug. 3, 1963, 38/ 41,499, 38/415410; Aug. 19, 1963, 38/ 43,395 4Claims. (Cl. 101-1282) This invention relates to stencil duplicatingtechniques and more particularly to a novel method of preparing stencilswherein stencil sheets are perforated by utilizing radiant rays.

In the conventional stencil duplicating technique desired characters,figures and patterns are perforated by writing the contents ofmanuscripts with a burin upon Waxed stencil papers which are placed onflat files. Alternatively these contents of manuscripts are type writtenupon stencil papers having a plastic film thereon. Both of these priorart methodsrequire many times, labours and skilled operators. Whilethere has been proposed another method of perforation which utilizesphotosensitive stencil sheets, this method has many defects that it mustbe carried out in dark rooms, and can not be perforated unless developedby a process similar to that of ordinary photograph art which requirestroublesome procedure of treating the stencil papers with a solvent. Inaddition, the resulted stencil sheet has poor storage ability. Stillanother approach of perforating stencil sheets is to use spark dischargebut this method not only requires long working time but alsonecessitates to use expensive stencil papers and perforating apparatusof com plicated construction which, of course, is liable to get out oforder.

It is an object of this invention to eliminate various defects mentionedabove and to provide a novel method of perforating desired characters,figures, codes, patterns, photographs or the like through stencil sheetsin a short time and with less effort at high efiicien-cy.

A further object of this invention is to provide a new and improvedmethod of easily perforating stencil sheets without any skil but byusing simple apparatus.

Still further object of this invention is to provide stencils capable ofproviding clear stencil duplications.

Another object of this invention is to provide a method of perforating anovel stencil sheet upon which characters, figures or patterns can beprinted by stencil duplicating process.

Yet another object of this invention is to provide a novel method ofeasily perforating characters, figures or patterns which are identicalwith those contained in manuscripts.

A still further object of this invention is to provide a novel methodwherein characters, figures or patterns are presented directly upon thesurfaces of stencil sheets and then perforated by simple means.

Further objects and advantages of this invention, may best be understoodby referring to the following description taken in connection with thedrawing.

It is to be understood that the term stencil duplication used herein notonly includes conventional method of printing by using rotary presses orhand presses wherein printing is effected by printing ink whichpenetrates through perforations of stencil sheets but also broadlycovers various methods of printing (or sometimes called as method ofduplicating) which utilize perforations through stencil sheetsrepresenting characters, figures, patterns or the like, such as a methodwherein adhesive powders are deposited upon sheet materials to beprinted such as papers after passing through perforations of stenoilsheets, a method wherein colored stencil sheets are utilized togetherwith diazo photosensitive papers, blue print sensitive papers and thelike methods.

In addition to common characters, figures, patterns and combinationsthereof, it is also intended to cover codes, photographs, pictures andcombinations thereof by the terms, characters, figures and patterns usedherein.

Further it is to be understood that by the term stencil sheet usedherein is meant to designate a material from which stencils aremanufactured for carrying out said stencil duplicating process so thatit should be interpreted in broader sense to include such materialswhich differ substantially from well known stencil paper for preparingstencils in contents, appearance, and material.

Briefly stated, this invention contemplates to provide a method ofpreparing stencils for use in stencil duplication characterized byirradiating radiations onto a heat sensitive stencil sheet which issuperposed upon a manuscript containing requisite characters, figures orpatterns or onto a heat sensitive stencil sheet upon which thecharacters and the like are directly represented, and causing saidstencil sheet to respond to heat generated by said characters, figuresor patterns by absorbing said radiations so as to provide perforationsthrough said stencil sheet which are nearly identical with saidcharacters, figures or patterns.

The following specific examples of this invention are given by referringto the accompanying drawings, in which FIG. 1 is a transversal sectionalview of an apparatus suitable to be utilized in carrying out thismethod;

FIG. 2 is an enlarged perspective view of a portion of a stencil sheetutilized in this invention;

FIG. 3 is an enlarged perspective view of a portion of another stencilsheet utilized in this invention; and

FIG. 4 is an enlarged perspective view with one part broken away, of aportion of still another stencil sheet utilized in this invention.

Referring now to the accompanying drawing, there is shown in FIG. 1 abox like platform 11 to support a perforating apparatus (not shown)containing an elongated tubular infrared ray lamp 12 which is adjustablefor horizontal movements by means provided outside of the platform 11. Aglass plate 13 transparent to infrared rays is fit in the upper openingof the platform 11 to support a silk screen of about 50 to meshes.

A stencil sheet 15 as shown in FIGS. 2 to 4 inclusive is tinted with acolor that exhibits poor absorption to infrared rays or transparent tosuch rays.

FIG. 2 shows the simplest form of the stencil sheet comprising a singlelayer of heat shrinkable film, having a thickness of about 15 microns,such as stretched polypropylene resin film and a film of copolymer ofvinylidene chloride and vinyl chloride.

FIG. 3 shows a modified stencil sheet which was prepared by mixing heatshrinkable resinous fibers 21 such as nylon or polyethylene resin fibersand base fibers 22 which do not shrink at temperatures at whichshrinkage of said resinous fiber 21 occurs, such as fibers used as a rawmaterial for making Japanese papers, in the ratio of 40% of the formerand 60% of the latter, by weight, and then shaping them into papershaving a thickness of about 50 microns. As the heat shrinkable resinousfiber, polypropylene fibers, and fibers prepared from a copolymer ofvinylidene chloride and vinyl chloride may be used in addition topolyethylene fibers mentioned above. Also in addition to the abovementioned fibers, long fibers of manila hemp, asbestos fibers, glassfibers and the like may be used as the base fibers. Further said basefibers may be embedded in heat shrinkable resinous material to form asheet.

A modified stencil sheet illustrated in FIG. 4 comprises a film of saidheat shrinkable resin 23 and a porous supporting sheet 24 cementedthereto which does not change its state at said shrinking temperatures.While the supporting sheet 24 may be bonded to the heat shrinkableresinous film 23 by means of heating or adhesive material, when usingadhesive material it should be applied as a film having a thickness assmall as possible. When a copolymer of vinylidene chloride and vinylchloride sold under the trade name of Saran film is used as the heatshrinkable resinous film 23 and tengujo paper (Japanese coarse tissuepaper) as the supporting sheet it is advantageous to make the thicknessof the former to be about microns and that of the latter about microns.As the heat shrinkable resinous film, may be used polyethylene andpolyester resin film while as the supporting sheet may be used pulp,woven fabric, non-woven fabric, fine meshed screen not sensitive to heatand the like.

In carrying out this invention, as shown in FIG. 1 a manuscript 16 isplaced upon the stencil sheet 15 and then a disc 17 of elastic materialformed with a reflective surface on its lower surface or a lower surfaceof a color having poor absorption property towards infrared rays issuperposed upon the manuscript, a portion of the periphery of said disc17 being clamped to the platform 11 to firmly hold the stencil sheet 15against the manuscript. The stencil sheet shown in FIG. 1 is of the typethat has been described in connection with FIG. 3. The manuscriptemployed is of the ordinary type that contains the matter to bereproduced such as black characters, figures or patterns which arewritten on a white paper. Any type of type written or hand writtenmanuscript could be used so long as characters, figures or patterns arewritten or printed on a sheet of a color having 'poor absorptionproperty towards infrared rays with an ink of a color having goodabsorption property towards infrared rays.

After assembling, the ultrared ray lamp 12 is lighted and is then movedhorizontally from one side to the other of the platform 11 to irradiateboth of the stencil sheet 15 and the manuscript 16 through the screen14, In this case, care should be taken to move the infrared ray lamp 12at a relatively high speed of about 3 to 6 cm./sec. to irradiate for arelatively short interval of time so that the temperature of theportions of the stencil 'sheet 15 corresponding to the characters,figures or patterns represented on the manuscript 16 can rise to about170 C. Under such condition, as the light source is moved, the wholeirradiated surface of the stencil sheet 15 will successively receive theinfrared rays as well as radiant heat emanated from the infrared raylamp to cause heat shrinkage of the first stage. Simultaneouslytherewith, the portions of the stencil sheet 15 corresponding to thecharacters, figures or patterns represented on the manuscript will beheated stronger than the remaining portions due to their high absorptionof infrared rays. As a consequence portions that correspond tocharacters, figures or patterns on the manuscript 16 will fuse anddecompose partially, this in conjunction with the said shrinkage of thewhole irradiated surface of the manuscript will make perforations ofsubstantially identical configurations as those of the characters,figures or patterns on the manuscript.

Perforations thus formed tovrepresent the characters, figures orpatterns are in the form of an asembly of small perforations which arereinforced by a grid structure comprising portions of the stencil sheetremaining unfused due to the shielding action of the screen 14 againstinfrared rays. As a result, even when the areas of the characters,figures or the patterns are too large, breakage of the stencil papercould be prevented effectively. In addition, during printing operation,too much penetration of the printing ink can also be effectivelyprecluded.

It is to be understood that it is not always necessary to use a screenin the perforating apparatus when a stencil paper shown in FIG. 3 or 4is utilized. With such a stencil sheet the supporting fiber or thesupporting sheet will remain in the portions which have been perforatedto effectively prevent breakage of the stencil sheet and excessivepenetration of the printing ink. Stencil sheets including suchsupporting member as supporting fibers or supporting sheet have largemechanical strength even after perforation so that they can be handledeasily because such supporting member does not undergo thermal change.Where use is made of a stencil sheet comprising a heat shrinkableresinous film and a supporting sheet which are bonded together by meansof a binder the thin film of the binder is also perforatedsimultaneously with the heat shrinkable resinous film.

Upon completion of perforation the stencil sheet is removed from theplatform together with the manuscript and is then separated therefrom.Thereafter the completed stencil can be used in a hand or rotaryprinting press to print with a printing ink in the same way as thestencils that have been perforated by the well known method.

While in the preceding description the invention has been stated to usea manuscript, it should be understood that this invention is by no meanslimited to the use of manuscripts. Thus, instead of superposing astencil sheet and a manuscript the matter to be reproduced such as,characters, figures or patterns may be directly typewritten or handwritten on the surface of a stencil sheet with an ink or pencil or acolor having high absorption towards infrared rays. Alternatively,powders which have high infrared ray absorption and can be easilyconverted by heat may be directly deposited on the surface of thestencil by the electronic photograph technique to represent charactersand the like.

The heat shrinkable resinous film utilized in the stencil papers shownin FIGS. 2 and 4 is made of a film of a copolymer of vinylidene chlorideand vinyl chloride which has been subjected to stretching treatment(generally termed as infiation process). However, if the heatshrinkability'of the film'is to large, the resolution thereof willbecome excessive so that the reproduced characters and the like wouldnot be clear. Thus, it is advantageous to increase the resolution of thestencil after perforation by subjecting it to a slight heat shrinkagetreatment whereby to suitably adjust its remaining heat shrinkability.It is desirable to adjust this remaining shrinkability such that thestencil paper will shrink by about 2 to 3 mm., both longitudinally andtransversally, when a test piece of the stencil sheet, 20 cm. x 20 cm.,is irradiated by an infrared ray lamp .at a rate of 3 to 4 cm./sec. in aperforating machine shown in FIG. 1 in a manner similar to perforationof a stencil sheet by utilizing a manuscript. This pretreatment can alsobe applied to the stencil paper shown in FIG. 3.

There are four pretreatment processes as follows:

(1) To move said film, under slight tension and under no pressure, topass closely around the surfaces of several metallic heated rolls. Thetemperature of the rolls is varied from about 60 C. at the first roll toabout 100 C. at the final roll, and the speed of the film is selected tobe about 15 to 30 m./sec.

(2) To pass the film through a bath of hot water at a speed such that itwill be dipped in the bath for about 17 seconds.

(3) To hold a rolled film in a constant temperature room, a vapor bathroom or in a warm water, respectively maintained at 50 C. to C., for 5to 10 hours.

(4) To move the film, under no pressure and under a slight tension, at aspeed of about 5 to 25 cm./sec., through an infrared ray heating roomwhich is preheated to about 80 C.

Usually the weight ratio between vinylidene chloride and vinyl chloridecomprising a heat shrinkable film for stencil papers is about 80% :20%.However by changing this ratio to'81 to %:19 to 5%, or by increasing thepercentage of vinylidene chloride content clear and sharp perforationscan be produced. By increasing the content of vinylidene chloride beyond84% results in the same excellent resolution as that of the pretreatedstencil paper.

It is also contemplated to use other radiations such as high frequencyelectromagnetic waves, radiations emanated from radio isotopes and thelike in addition to infrared ra s.

There are two methods of irradiation as follows:

In one case wherein a stencil paper with characters and the like aredirectly represented thereon is to be perforated, irradition may begiven to either side of the stencil paper.

In the other case wherein a manuscript is used and the stencil sheet isto be perforated according to the contents of the manuscript, thesurface of the manuscript and the heat sensitive surface of the stencilpaper should be intimately contacted. Opposite surfaces of stencilsheets shown in FIGS. 2 and 3 are physically the same so that either oneof these surfaces can be closely contacted with the manuscript. In thiscase, an assembly of the stencil sheet and the manuscript which aresuperposed in intimate contact relation is subjected to irradiation. Ifthe manuscript is rather thick so that radiations tare difiicult to passthrough it, the irradiation should be made from the side of themanuscript whereas if the manuscript is rather thin to permit radiationsto pass easily therethrough, and if characters and the like arerepresented on only one side of the manuscript, then irradiation may bemade either from the side of the manuscript or the side of the stencilpaper.

Even if thin manuscripts are employed, as they usually containcharacters and the like on both sides thereof, irradiations must be madefrom the side of the stencil paper in order to perforate it.

It should be understood that stencils which have been perforated inaccordance with the method of this invention can be utilized not only ina method of printing which utilizes a printing ink, but also in variousother methods of printing including a perforated stencil printing methodwherein solid particles are transferred to and deposited on a printingpaper through perforations in the stencil and a method wherein a stencilpaper tinted with red color and hence is opaque to ultraviolet rays isutilized to print on a paper by means of diazo photosensitive system bypermitting ultraviolet rays to pass only through perforations.

While in the above embodiments an infrared ray lamp was moved withrespect to a fixed stencil paper but it will be clear to those skilledin the art that the stencil or a compact assembly of a stencil and amanuscript may be moved with respect to the source of radiation. It willalso be understood that an infrared spot light source may be utilized asthe source of irradiation. More particularly, in this case infrared rayirradiation can be made while'holding stationary both of the ligthsource and a stencil paper with characters, figures or patterns directlyrepresented thereon, and also a manuscript when it is used.

In order to provide intimate contact between a stencil sheet and amanuscript, air may be used or they may be urged against a support bytension, as has been the practice in the prior art.

While the invention has been explained by describing particularembodiments thereof, it will be apparent that improvements andmodifications may be made without departing from the scope of theinvention as defined in the appended claims.

What is claimed is:

1. A method of preparing a stencil sheet for use in reproducing blackmaster material comprising the steps of heat stretching a stencil sheethaving thereon a heat shrinkable fihn of a copolymer of vinylidenechloride and vinyl chloride to the extent that said sheet will shrinkbetween about two to three millimeters for a sheet of about twentycentimeters square, superposing said sheet upon the material to bereproduced, irradiating said stretched sheet with infrared rays from alamp moving at between about three to six centimeters per second acrossthe sheet so as to perforate the sheet, the shape of the perforationscorresponding to the master material to be reproduced.

2. The method according to claim 1 wherein the Weight ratio betweenvinylidine chloride and vinyl chloride is about parts of vinylidinechloride and 20 parts of vinyl chloride.

3. The method according to claim 2 wherein ratio of vinylidine chlorideto vinyl chloride is about parts to 5 parts.

4. The method according to claim 3 wherein a porous supporting medium,not affected by the action of the heat thereon is bonded to said sheet.

References Cited by the Examiner UNITED STATES PATENTS 1,456,794 5/1923Gestetner 101--l28.3 2,699,113 l/1955 Hoover 10ll28.4 2,808,777 10/1957Roshkind 101128.2

DAVID KLEIN, Primary Examiner.

1. A METHOD OF PREPARING A STENCIL SHEET FOR USE IN REPRODUCING BLACKMASTER MATERIAL COMPRISING THE STEPS OF HEAT STRETCHING A STENCIL SHEETHAVING THEREON A HEAT SHRINKABLE FILM OF A COPOLYMER OF VINYLIDENECHLORIDE AND VINYL CHLORIDE TO THE EXTENT THAT SAID SHEET WILL SHRINKBETWEEN ABOUT TWO TO THREE MILLIMETERS FOR A SHEET OF ABOUT TWENTYCENTIMETERS SQUARE, SUPERPOSING SAID SHEET UPON THE MATERIAL TO BEREPRODUCED, IRRADIATING SAID STRETCHED SHEET WITH INFRARED RAYS FROM ALAMP MOVING AT BETWEEN ABOUT THREE TO SIX CENTIMETERS PER SECOND ACROSSTHE SHEET SO AS TO PERFORATE THE SHEET, THE SHAPE OF THE PERFORATIONSCORRESPONDNG TO THE MASTER MATERIAL TO BE REPRODUCED.